1. Field of the Invention
The present invention relates to a liner movement rolling guide apparatus of a feed table apparatus for movably supporting a movable table with respect to a bed, and to a method for manufacturing a rolling bearing roller.
2. Description of the Art
A fundamental structure of a linear movement rolling bearing includes, as shown in FIGS. 3 and 4, a guide rail 1 fixed to a base 2 and another guide rail 3 fixed to a movable table 4. A multiplicity of rollers 5 retained in a retainer 6 are interposed between the guide rail 1 and the guide rail 3. In this respect, the rollers 5 are of the cross roller type in which axis lines of adjacent rollers intersect with each other at an angle of 90 degrees. However, there also is a linear roller type in which the axis lines of the rollers 5 are in parallel with one another. The fundamental structure of this linear movement rolling bearing is shown in U.S. Pat. No. 3,778,121.
However, in the prior art linear movement rolling bearing 7, the rollers 5 are not constrained between the guide rails 1 and 3 in the longitudinal direction. As a result, relative positions between the guide rails 1 and 3 and the retainer 6 are deviated little by little and, ultimately, the retainer 6 will slip from the guide rails 1 and 3. This phenomenon is called a micro-slip phenomenon. In order to prevent the micro-slip phenomenon, it has been well known to form rack teeth in the guide rails 1 and 3 and, also, pinion-like teeth in an outer peripheral surface of the rollers 5 to thereby make associated members engage each other. Alternately, the movements of these members are corrected by a wire or the like. However, a problem is involved in these measures in that the structure becomes complicated and the manufacturing costs are increased. In addition, each of the associated members is excessively constrained.
The inventors of the present application conducted various experiments and analyses to clarify the cause of the micro-slip phenomenon and found that the cause of the micro-slip phenomenon resides in a slip between the rollers and both of the guide rails with which the rollers are in contact while rolling. Based on this knowledge, bearing rollers were invented which solve the above-mentioned problems by specifying a relationship between surface roughness in a circumferential direction and surface roughness in an axial direction of an outer peripheral surface of the rollers to suppress the slip of the rollers with respect to both of the guide rails.
Furthermore, when a conventional surface treatment is applied to the roller in order to manufacture a roller which has a specific relationship between the surface roughness in the circumferential direction and the surface roughness in the axial direction of the outer peripheral surface, the following problem was revealed. That is, in a grinding finishing of an outer peripheral surface of a roller material which is performed while rotating the roller material, when the surface roughness in the circumferential direction is increased, the surface roughness in the axial direction becomes further increased as compared with that in the circumferential direction. As a result, a problem arose in the operability and the durability of the bearing roller. Moreover, when the roller material which has been ground is further subjected to tumbling, the roughness of the peripheral surface formed during the grinding work and the low dimensional accuracy are adversely effected, and a desired surface condition cannot be stably achieved.